The implantation of biomaterials into soft tissues leads to the development of the foreign body response (FBR) that can interfere with the function of the implant and eventually lead to implant failure. In general, due to the FBR a largely avascular and dense collagenous capsule forms around biomaterials and scaffolds. A hallmark of the FBR is the formation and persistence of foreign body giant cells (FBGC) on the surface of the implant, a process that is indicative of a chronic inflammatory response. In addition, FBGC have been shown to cause extensive surface damage to a variety of biomaterials and cause the release of microparticles that can have toxic effects. Furthermore, a role for FBGC in promoting biomaterial encapsulation has been proposed. Thus, unlike a wound healing response that is self-limiting, the FBR can last for the duration of the implantation period. Despite the prominence of FBGC at implantation sites, little is known about their formation in vivo. We have found that MCP-1-null mice display compromised FBGC formation that is associated with reduced biomaterial damage. In Specific Aim 1 of this proposal we aim to fully characterize the FBR in the MCP-1-null mice. In Specific Aim 2 we will focus on monocyte recruitment and FBGC formation and, by selective temporal inhibition of MCP-1, we will dissect its contribution to these processes. In Specific Aim 3 we will utilize an in vitro assay to investigate the molecular and biochemical cues that are influenced by the lack of MPC-1. Finally, in Specific Aim 4 a gene delivery approach will be employed to limit FBGC formation, increase foreign body capsule neovascularization and shift the FBR towards a wound healing phenotype. It is expected that a shift towards a wound healing-like response should enhance biocompatibility by preventing damage and extending the lifespan of implants. Overall, this application proposes a novel approach to target the FBR, primarily by the selective targeting of host-derived molecular processes.